header{
    display: block;
    margin: 0 auto;
    width: 500px;
    text-align: center;
}
header h1{
    font-family: Arial;
    font-size: 60px;
    font-weight: bold;
}
header #newgamebutton{
    display: block;
    margin: 20px auto;
    width: 100px;
    padding: 10px 10px;
    background-color: #8f7a66;
    font-family: Arial;
    color: white;
    border-radius: 10px;
    text-decoration: none;
}
header #newgamebutton:hover{
    background-color: #9f8b77;
}
header p{
    font-family: Arial;
    font-size: 25px;
    margin: 20px auto;
}
#bug{
    font-size: 15px;
    margin: 10px auto;
    color: green;
    text-align: left;
}
#grid-container{
    width: 460px;
    height: 460px;
    padding: 20px;
    margin: 50px auto;
    background-color: #bbada0;
    border-radius: 10px;
    position: relative;
}
.grid-cell{
    width: 100px;
    height: 100px;
    border-radius: 6px;
    background-color: #ccc0b3;
    /*可根据top,left确定位置*/
    position: absolute;
}
.number-cell{
    border-radius: 6px;
    font-family: Arial;
    font-weight: bold;
    font-size: 60px;
    line-height: 100px;
    text-align: center;
    position: absolute;
}